Chapter 3. Tune sendmail with Compile-Time Macros

For most users, the default sendmail that is produced by running Build is perfectly suitable. For others, however, support for certain desirable features—such as hesiod, LDAP, or NIS—will have to be added. The open source distribution of sendmail has many such support items that you can include or exclude from your compiled binary using compile-time macros.

What’s New with V8.13

V8.13 has introduced six new compile-time macros:

  • The new SOCKETMAP compile-time macro enables use of the new socket database-map type (Section 3.1.1 [V8.13]).

  • The new SM_CONF_LDAP_INITIALIZE compile-time macro (Section 3.1.2 [V8.13]) if set, declares that the ldap_initialize(3) routine exists in your LDAP library.

  • The new NEEDINTERRNO compile-time macro, if set, says that errno is not declared in your system’s errno.h file.

  • The new SM_CONF_POLL compile-time macro causes poll(2) to be used instead of select(2) in the Milter library.

  • The new HASCLOSEFROM compile-time macro may be defined if your system has the closefrom(3) C-library function.

  • The new HASFDWALK compile-time macro may be defined if your system has the fdwalk(3) C-library function.

The SOCKETMAP Compile-Time Macro

The SOCKETMAP compile-time macro enables use of the new socket database-map type (Section 23.1.5 [V8.13]). Define SOCKETMAP inside your Build m4 file with a line like this:

               APPENDDEF(`confMAPDEF´, `-DSOCKETMAP´)

If you use a vendor supplied sendmail program, you may check to see whether it includes SOCKETMAP support by running a command like the following:

% /usr/sbin/sendmail -bt -d0.4 < /dev/null | grep SOCKETMAP

If a line of text is printed containing SOCKETMAP, you indeed have support for it. If not, you will either need to contact your vendor or download and build open source sendmail.

The SM_CONF_LDAP_INITIALIZE Compile-Time Macro

When sendmail is built with LDAPMAP defined (3.4.19[3ed]), LDAP database-maps are available for use. If the LDAP library contains an ldap_initialize( ) routine, and if this SM_CONF_LDAP_INITIALIZE macro is defined, ldap_initialize( ) is called if your LDAP server supports direct use of URIs.

Note that LDAP URIs can still be used even if SM_CONF_LDAP_INITIALIZE is not set, but the scheme:// in (scheme://host:port/...) is ignored. Therefore, if SM_CONF_LDAP_INITIALIZE is not available, the scheme ldap:// is always used, but the schemes ldaps:// and ldapi://, if used, may result in an error.

For most LDAP libraries, SM_CONF_LDAP_INITIALIZE will be set properly for you.[2] But in the event it is improperly set, you may define it with the following and then rebuild sendmail:

               APPENDDEF(`conf_libsm_ENVDEF´, `-DSM_CONF_LDAP_INITIALIZE´)

[2] It is automatically defined if LDAP_OPT_URI is defined by the LDAP include files, which is how OpenLDAP implements ldap_initialize( ).

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